Project Abstract Sensory-motor processing must accommodate varying environmental conditions and the internal physiological state of an animal to quickly assign positive, neutral, or negative valence values. Valence values have been shown to change through learning-dependent plasticity mediated by the action of neuromodulators. However, little is known about whether or how neuromodulators mediate rapid changes in the valence of hard-wired sensory pathways. In this proposal, I focus on a particular behavioral valence switch in the model system Drosophila melanogaster. I first establish that in flying flies, the valence of a small visual object switches from negative to positive within seconds in the presence of an appetitive food odor. To uncover the neural mechanisms underlying this odor-induced visual valence switch, I propose the following aims: 1) Identify the biogenic amines involved in odor-induced visual valence switch with gain-of-function and loss-of-function experiments using optogenetics and genetic silencing of known aminergic pathways. 2) Identify visual neurons whose receptive field properties are modified by biogenic amines using optogenetics, immunohistochemistry and in vivo calcium imaging. 3) Determine the connectivity between aminergic neurons and visual neurons using a series of behavioral, anatomical and physiological techniques. Understanding valence switching at the molecular and cell-circuit levels of organization is crucial to developing a comprehensive understanding of brain function. Since there are few productive research models in this area, the results will likely provide better understanding of the role of biogenic amines relevant to brain illness and injury that generalizes to vertebrate animals.